1. Field of the Invention
The present invention generally relates to microfabrication of data storage mechanisms and, in particular, to a system and method for forming integrated data storage mechanisms that are actuated by electrostatic forces.
2. Related Art
In current computer systems, data is frequently stored and retrieved respectively to and from memory while forming and executing application programs. The memory used to store the information can be any medium having properties that can be altered in order to reflect data patterns. For example, a magnetic type of material is frequently used as the data storage medium, and as known in the art, the polarization of magnetic material can be set by passing magnetic fields through the material. When it is desirable to store data, a device sets the polarization of particular locations on the medium to reflect the data pattern being stored. Later, when it is desirable to retrieve the stored data, the device can return to the particular locations on the data storage medium and analyze the polarization of the magnetic material to determine the data pattern of the data being retrieved. Therefore, the device used to store and retrieve data should be capable of moving to particular locations on the medium with a high level of precision and accuracy.
In tip-based data storage, the data storage medium is formed at a certain distance from one or more tips, which are capable of storing and retrieving data from the medium. The elements forming the tips are usually small conical structures, fabricated by the techniques of micromachining. The medium may be directly in contact with the tips as in the cases of thermomechanical data storage or ferroelectric phase change data storage or may be separated from the tips as in the cases of near-field optical data storage or field-emission data storage. Similar to magnetic data storage, the medium is usually moved relative to the tips in order to access data. The tips can transmit a laser or an electron beam to alter the properties of the medium in order to reflect the bit pattern of the data being stored. Therefore, the material of the medium is not necessarily magnetic and can be any material with properties capable of being altered by transmissions from the tips.
As can be appreciated by one skilled in the art, it is desirable to microfabricate data storage devices in order to reduce the costs of manufacturing and to reduce the size of the data storage devices. Furthermore, microfabrication of data storage devices can be facilitated if electrostatic actuators can be utilized to actuate the data storage devices. In this regard, electrostatic actuators typically utilize electrodes to generate electrical fields that can be used to supply the necessary forces for moving the data storage medium, and these electrodes can be easily formed through microfabrication techniques. Additionally, electrostatic actuators can operate at relatively low power. Therefore, it is often desirable to use electrostatic actuators for actuating microfabricated data storage devices.
However, a problem with most common electrostatic actuators is that relatively high drive voltages (sometimes more than 100 Volts) are required for operation. Moreover, the overall area and, hence, the cost of the storage device are determined primarily by the area required by the electrostatic actuators. In addition, the dissimilar materials in most conventional electrostatic actuators have varying thermal expansion properties. Therefore, the components of the actuators-bend due to temperature changes, and as a result, the components of the data storage device are separated by larger distances (requiring higher voltages for actuation) in order to accommodate for the bending. Consequently, the components of the data storage device require larger areas and higher voltages due to the varying thermal expansion properties of the dissimilar materials within the electrostatic actuators.
Furthermore, many electrostatic actuators do not easily allow motion in a two-dimensional plane, which is desirable for data storage applications. Due to the difficulties of microfabricating suitable electrostatic actuated storage devices, most conventional tip-based storage devices refrain from using electrostatic actuators.
Thus, a previously unaddressed need exists in the industry for a system and method for efficiently forming a tip-based electrostatic storage device capable of production through microfabrication techniques.
The present invention overcomes the inadequacies and deficiencies of the prior art as discussed above. Briefly described, the present invention provides a system and method for efficiently microfabricating integrated data storage mechanisms that are actuated by electrostatic forces.
In accordance with the present invention, a plurality of data storage media are integrated within a data storage system. Each data storage medium is coupled to a respective movable support that is coupled to a plurality of flexures. The plurality of flexures significantly resists motion of the medium in a first predetermined direction and allows the medium to move in a second predetermined direction. The flexures are preferably comprised of a plurality of interconnected panels that are coupled to the movable support and to a layer of a microfabricated structure in order to support the data storage medium and the movable support.
The movable support coupled to each data storage medium is also coupled to a plurality of electrodes. Preferably, the plurality of electrodes is coupled to a surface of the movable support opposite of the surface of the movable support coupled to the data storage medium. A second plurality of electrodes generates electrical fields that interact with electrical fields generated by the electrodes coupled to the movable support, thereby causing the movable support and, hence, the storage medium to move in a desired direction. Preferably, the second plurality of electrodes are formed substantially parallel to the plurality of electrodes coupled to the moveable support in order to define a surface actuator.
In accordance with another feature of the present invention, one or more tips are formed on another microfabricated structure that is bonded to the microfabricated structure containing the data storage media. Each tip is formed adjacent to a respective data storage medium and is configured to store data on the respective data storage medium. Preferably, the two microfabricated structures are joined via a bond having palladium elements bonded to silicon elements.
In accordance with another feature to the present invention, a gasket is formed between the two microfabricated structures in order to seal the data storage media within the data storage system. The gasket is preferably fused to one of the wafers during the bonding of the two microfabricated structures.
The present invention can also be viewed as providing a method for microfabricating a data storage system. Briefly described, the method can be broadly conceptualized by the following steps: forming a first plurality of electrodes on a surface of a wafer; forming a sacrificial layer on the first plurality of electrodes; forming a second plurality of electrodes on the sacrificial layer; forming a support layer on the sacrificial layer; forming a data storage medium on the support layer; removing portions of the support layer to form flexures that allow the data storage medium to move in a predetermined direction; and removing material from the sacrificial layer.
The present invention has many advantages, a few of which are delineated below, as mere examples.
An advantage of the present invention is that an electrostatically actuated data storage system can be efficiently microfabricated.
Another advantage of the present invention is that production costs of data storage systems can be significantly reduced.
Another advantage of the present invention is that data storage systems of smaller scale than those currently available in the art can be realized.
Another advantage of the present invention is that electrostatically actuated data storage systems can be operated at low voltages.
Another advantage of the present invention is that external vibrations felt by a data storage system can be easily damped out of the movement of a data storage medium within a data storage system because the frequencies of the moving elements are determined primarily by electrical potentials rather than mechanical spring constants and masses.
Another advantage of the present invention is that relatively high stress levels within a data storage system can be accommodated.
Other features and advantages of the present invention will become apparent to one skilled in the art upon examination of the following detailed description, when read in conjunction with the accompanying drawings. It is intended that all such features and advantages be included herein within the scope of the present invention, as is defined by the claims.